the defense says she had a long-term heart condition and that was the cause of her death. >> i didn't find any evidence. >> reporter: cardiologist said from his analysis she was in relatively good health and there was no natural reason she should have been found unconscious in her bathtub in april of 2007. >> in chest pain. she had no symptoms that suggest that she had a significant problem. >> are doctors unique in their ability to commit homicide? >> objection. >> reporter: prosecutors dropped that bombshell but prevented from questioning dr. joshua perper about his book "when doctors kill, who, why and how" but that did not prevent him from giving his medical opinion. >> so your examination of the lungs and the microscope pick slides of the lungs. >> yes. >> support a finding of drowning? >> yes. >> reporter: and on cross examination they got the doctor to admit possibly michelle macneill died of naturally occurring heart disease. now, erin, next week closing arguments, dell rations maybe even a verdict. >> wow, obviously going to be eyes on that, thank you. we'll see you monday an